Making calls in Gmail is great, but previously you were only to make and receive only one call at a time. Google lifted that restriction today and now you can juggle multiple calls at once. This doesn't mean conference calling, but rather a call waiting-like feature. When you get another call, you can put your current one on hold to answer it. Pressing a resume button will let you switch back to another active call. This works for all call types, although you can only have two calls to physical phones happening at one time.